Grip tip

ABSTRACT

A spiral-wound tip is presented for use on a walking assistance device, a robotic arm or digit, or other device needing a slip-resistant point of contact with its environment. The tip is constructed by winding a sheet of rubber or other elastic material into a spiral plug. The plug can be mounted within a hole at the extremity of a device. Alternatively, the sheet can be wrapped around the exterior of the extremity. The lamina of the spiral-wound plug separate upon impact with an object, increasing the gripping power of the tip.

CLAIM OF PRIORITY

This application is a divisional application of U.S. patent applicationSer. No. 10/792,058, filed on Mar. 3, 2004, which in turn claimed thebenefit of provisional patent application U.S. Ser. No. 60/451,567,filed on Mar. 3, 2003.

FIELD OF THE INVENTION

This invention relates to the field of tips for use with a robotic leg,a gripper, or digit, or for use with walking aids, such as canes andcrutches. More particularly, the present invention relates to a tip thatprovides better grip when engaged with a surface by having aspiral-wound plug.

BACKGROUND OF THE INVENTION

It is well known in the prior art to provide canes, crutches, and otherwalking aids with a tip made from natural rubber, polyurethane, orsimilar material. This tip engages with the walking surface, and ideallyhelps absorbs impact and provides greater gripping than that which wouldbe provided if the walking device directly engaged with the walkingsurface.

Typical prior art tips incorporate a tread design on the tip's bottomsurface to assist in both of these functions. One well-known treaddesign utilizes concentric ridges protruding from the bottom surface ofthe tip. Alternative prior art designs include parallel linear ridges,spikes for gripping icy surfaces, and protrusions shaped like piepieces. Unfortunately, none of the tread designs found in prior art tipsprovides adequate gripping power on wet or otherwise slippery surfaces.

Similarly, in the field of robotics it is often necessary to increasethe gripping power of a tip. For instance, robots that propel themselvesby moving two or more legs need to minimize the slippage that occurs aseach leg contacts the walking surface. Automated “arms” or “hands” or“fingers” that grasp, push or pull an object also need an ability togrip an object or surface. In these circumstances, it is vital tomaximize the amount of friction obtained by the robotic device againstsurfaces. Unfortunately, prior art techniques of placing a rubber cap onthe leg or finger often entails significant effort and expense, andfails to achieve satisfactory results.

What is needed is a way to maximize the gripping power of such tipswhile minimizing the cost and difficulty of tip construction.

SUMMARY OF THE INVENTION

The present invention overcomes the limitations in the prior art byproviding a tip that is easily constructed and provides improvedgripping performance on slippery surfaces. This is accomplished bytightly winding a sheet of material into a spiral-wound “plug.” Thisplug can then be attached to a device such as a walking aid, roboticarm, and the like. Preferably, the plug is made from a sheet of rubberor rubber-like material, having a length that is greater than its width,and a width that is at least ten times greater than its thickness.

The attachment can be made by inserting the plug into a receiving holeat the terminal end of the device. Ideally, a friction fit is obtainedby which the plug is fixed to the device without the aid of an adhesiveor a mechanical fastener. Although such a friction fit is preferred, thepresent invention remains functional if the plug is otherwise attachedto the end of the device.

A second embodiment is also discussed in which the material is wounddirectly around the end of the device. In this way, the spiral-woundplug is on the exterior of the robotic appendage or walking aid, withsuch device serving as the core of the plug. This plug can be secured tothe device using an adhesive, which also serves to keep the plug in atightly wound spiral. Alternatively, a band can be used to secure theplug to the device.

In both embodiments, the plug creates layers or lamina that interactwith a surface in a unique manner. Upon contact with a surface, thelamina of the spiral-wound plug separate, increasing the gripping powerof the tip. The separation of the lamina is controlled by the spiralnature of the plug, thus distinguishing this separation from theseparation that might be achieved by a tread design having multiple,separating fingers. The separation of the lamina is especiallypronounced when the angle of impact between the device and the surfaceis less than ninety degrees.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view of a grip or tip of the present invention.

FIG. 2 is a top plan view of a sheet of material used to create the plugfor the grip of FIG. 1.

FIG. 3 is a side elevation view of the sheet of FIG. 2.

FIG. 4 is a perspective view of the sheet of FIG. 2 being rolled intothe plug found in the grip of FIG. 1.

FIG. 5 is a perspective view of the grip of FIG. 1 in use against asurface.

FIG. 6 is a cross-sectional view of the grip of FIG. 5 taken along planeA.

FIG. 7 is a bottom plan view of the contact surface of the grip of FIG.5, as indicated in FIG. 5 by arrow B.

FIG. 8 is a perspective view of an alternative embodiment of a grip ortip of the present invention.

FIG. 9 is a perspective view of a sheet of material being rolled intothe plug found in the grip of FIG. 8.

FIG. 10 is a top plan view of the sheet of material shown in FIG. 9.

FIG. 11 is a side elevation view of the sheet of FIG. 10.

DETAILED DESCRIPTION OF THE INVENTION

FIG. 1 shows a tip or grip 10 of the present invention. This embodimentof grip 10 is made from a spiral-wound cylinder or plug 12 that ismounted on the extremity of a device 14 that needs to grip a surface.The device 14 may be a prosthetic walking device such as a cane orcrutch, or a robotic element such as a limb, digit, gripper, or anotherrobotic component that uses a pad to contact something in itsenvironment. In fact, the device 14 may be any device that has need of aslip-resistant point of contact with its environment (the “environmentalpoint of contact”). As such, grip 10 can serve as a fingertip formanipulating other objects, as a gripper pad for grasping, or as afoot-surface for pedal locomotion.

The device 14 may be made of a variety of materials. Often it isnecessary to maximize the load carrying capacity of device 14 whileminimizing the weight of device 14. In these circumstances, device 14 isoften made of hollow tubing formed from metal, carbon fiber, or glassfiber. In applications where weight is not as significant an issue, thedevice 14 may be solid wood or metal. In any event, the material ofdevice 14 rarely provides sufficient grip with the environment tofunction without an attached grip 10.

The grip 10 of the present invention uses a spiral wound plug 12 toengage the environment. This construction results in the creation oflayers or lamina that remain separable and exhibit an extraordinaryability to conform to and exert frictional forces against environmentalsurfaces. Ideal materials from which to construct plug 12 arecharacterized by 1) a high coefficient of friction in relation to thesurfaces on which it will grip; 2) sufficient elasticity to allow thelamina to separate and more readily conform to the environment, and 3)sufficient durability to allow a reasonable service life. Butyl rubberhas been commonly used as a tip material for walking aids, and wouldfunction well as the material for plug 12. Polyurethane would be anotheracceptable choice. In fact, any material that has the three propertiesabove similar to or superior to that of rubber would make an acceptabletip 10 for the present invention. In fact, a durability that results inonly half the service life of rubber may be acceptable.

The dimensions of the grip 10 vary according to the forces involved inthe intended application, just as the dimensions of a tire are relativeto the size and weight of the vehicle on which it is mounted. Forexample, a grip 10 for the foot-pads of a robotic device the size of aman are best made in a diameter greater than an inch, using material forplug 12 similar in composition and thickness to that generally found inan automobile inner tube. A grip 10 for a walking cane is best made in adiameter less than an inch, using material for plug 12 similar to thatused in a standard bicycle inner tube.

The plug 12 is inset into a round hole 16 found in the end of device 14.The hole 16 could be the cylindrical space in the end of a piece oftubing, a ferrule attached to an otherwise solid appendage, or a cavitybored out with a drill. Generally, slightly more than half of the lengthof plug 12 is inserted into the hole with less than half of the plug 12extended past the end of device 14 to form the gripping surface. Theactual amount of the plug 12 that is embedded in the hole depends on theability to hold the plug 12 in place at the end of device 14 whilemaintaining the spiral-wound nature of the plug 12. Consequently, ifadequate means were available to secure the plug 12, it would be wellwithin the scope of the present invention to insert significantly lessthan half of the plug 12 within hole 16.

In the preferred embodiment, the plug 12 is fixed within hole 16 throughan interference fit. One way to accomplish this is to size the plug 12and hole 16 appropriately, and then compress the outer diameter of theplug 12 while inserting it into the hole 16. The expansion of the plug12 within hole 16 then creates the appropriate fit. Assuming the wallsthat form hole 16 have some elasticity, one might also expand the innerdiameter of the hole 16 during the insertion of the plug 12. Either way,the interference fit should securely attach the plug 12 to the end ofdevice 14. Alternative although less preferred methods of attaching plug12 to device 14 would be clear to one of skill in the art, includingthrough the use of an epoxy or other adhesive, or through a mechanicalattachment such as a screw or bolt.

The spiral-wound laminar plug 12 is made from a generally rectangularpiece of rubber-like material 20, such as that shown in FIGS. 2 and 3.The length 22 and width 24 of the rectangular material 20 are asadjusted as needed for the desired size of plug 12 for a given thickness26 of material 20. For example, a rectangular sheet 20 of butyl rubberthat is 3/64ths inches in thickness, 1 inch wide and 6 inches long issuitable for making a plug 12 for the foot of a small robotic device orfor the tip of a walking cane. A plug 12 for heavy equipment could bemade from a sheet a foot wide and a yard long, fashioned from an inchthick carbon-impregnated rubber such as is used in the tread of a trucktire.

For best results, the thickness 26 of sheet 20 is at least an order ofmagnitude smaller than its width 24, with a length 22 greater that itswidth 24. These dimensions facilitate the process of rolling it into aspiral cylinder plug 12. Stated otherwise, given that the material hasthree linear dimensions, length 22, width 24, and thickness 26, thelength 22 and the width 24 should each be at least ten times thethickness 26, with the length 22 greater than the width 24.

In the preferred embodiment, one corner of the rectangular sheet 20 isremoved at location 28 by cutting off the corner at approximatelyforty-five degrees. This location 28 will form the exposed outer cornerof the plug 12. Clipping the sharp ninety-degree corner off of location28 helps prevent this corner from flapping loose during use of grip 10.As seen in FIGS. 1 and 2, the amount removed from location 28 ispreferably such that, when the plug 12 is inserted in device 14, theremaining portion of side 30 is either wholly within hole 16 or does notsignificantly extend beyond hole 16.

In the preferred embodiment, sheet 20 is cut from new material of thedesired thickness 26 to form a rectangle of the appropriate length 22and width 24. However, good results can also be obtained by using asegment cut from a tube of rubber-like material, provided the thicknessof the tubing wall is an order of magnitude less than the diameter ofthe tube. All that is necessary is to flatten the tube segment into arectangle and proceed as if the material came from an originally flatsheet.

Sheet 20 is rolled to form the spiral plug 12, as is shown in FIG. 4.The diameter of the plug 12 created by the rolling is determined by thethickness of the material from which it is wound, the number of turns,and the size of the core, if any, around which it is wound.

To form a tight spiral, the plug 12 is normally rolled while the sheet20 is under length-wise tension. This is easily accomplished by layingthe rectangle down on a flat surface. One end is fixed or otherwise helddown so that tension can be applied to stretch the sheet 20. The otherend is then rolled up to form spiral plug 12. The tension applied tosheet 20 can be adjusted as desired during the rolling process.Significant changes to this length-wise tension will cause changes inthe width 24 of sheet 20. By selectively changing the width of sheet 20during the rolling process, one can obtain a convex, concave, or flatsurface on the end of the cylinder plug 12.

It is sometimes helpful to use an elongated segment of rubber as a“seed” 32 around which the spiral is formed. Ideally, this segment ofrubber tubing is approximately equal in length to the width 24 of therectangular sheet 20. The rubber seed becomes permanently incorporatedinto the plug 12 as its core 32.

When the entire length 22 of the rectangle 20 has been wound up into thespiral plug 12, the plug 12 must be bound to allow handling withoutuncoiling. For best performance, the separate lamina or layers of plug12 must remain substantially free of each other on at least one side ofthe plug 12. If adhesives are used to bind the spiral plug 12, care mustbe taken that adhesive does not bind the portions of plug 12 that willextend beyond hole 16 in device 14. If these portions of the plug 12layers were bound together, the resultant grip 10 would in effect besimilar to a solid cylinder of rubber with a standard tread design.Alternatively, an external wrap of tape or a tight-fitting rubber sleevecan be placed around the spiral plug 12 to enable the plug 12 to bestored and handled until mounting. This wrap can then be trimmed offafter the plug is mounted within device 14. The wrap can also functionto constrict the diameter of plug 12 for initial insertion into hole 16.

This manner of construction provides a financial advantage in themanufacturing process versus prior art gripping tips, as a manufacturercan create any size tip 10 quickly and economically, even for shortproduction runs. It is no longer necessary for a manufacturer to createa separate die or mold for each desired tip size, and the equipment tocast or mold rubber-like materials is no longer necessary. All that isnecessary is to have on hand sheets 20 of material having the desiredthickness 26. The sheets 20 can then be cut to the appropriate length 22and width 24 as needed

The grip 10 of the present invention also provides a significantperformance advantage over prior art tips. FIGS. 5 through 7 show adevice 14 having grip 10 of the present invention in use with an object50. The spiral-wound plug 12 of grip 10 provides the ideal contactsurface 40 with an object 50. The individual lamina or layers 42 thatcomprise the plug 12 separate when the surface 40 impacts the object 50,especially when the impact is at an angle less than ninety degrees.Unlike prior art grips where a superficial tread pattern is molded orcut into a solid rubber tip, the lamina 42 of the present invention areable to separate from each other. In addition, as shown most clearly inFIG. 7, the spiral nature of the lamina 42 that comprise surface 40 areunique in that they are linked together. As one lamina 42 moves, theypull upon and distort one another in adaptive ways. For instance, theoutermost lamina 42 is able to separate itself only so far from the restof the plug 12. This is unlike tread designs that contain trulyindependent fingers or treads.

The movement of the lamina 42 upon contact with object 50 results inmany contact edges and surfaces not bound together by the solidsubstructure of a tread in a prior art tip. This enables the separatelamina to individually move against each other, facilitating thetransition to exerting forces according to the static coefficient offriction. Direct comparison between the present invention grip 10 andsolid molded rubber caps of similar size suggests that the laminarconstruction of plug 12 produces effects significantly superior to thoseachieved with grooves and tread patterns cast, cut, or molded into arubbery surface.

Another benefit of mounting the spiral-bound plug 12 within hole 16 isthat it is possible to trim the contact surface to any depth withoutremoving the tread pattern. As wear occurs, the plug can be extendedfrom hole 16 and re-trimmed. It is also possible to alter the contactsurface 40 of grip 10 by cutting or otherwise shaping surface 40 afterthe plug 12 is mounted to the device 14. A straight cut parallel tosurface 40 will expose fresh rubber that should increase the grippingability of the surface 40. Because the separate lamina run through theentire body of the plug, cutting away material from the contact surfacehas no material impact on the skid-proof nature of the device.Alternatively, the surface 40 could be reshaped into a concave or convexsurface. A convex surface 40 would maximize the number of lamina 42 thatfirst impact an object 50 when the grip 10 impacts the object 50 at lessthan a ninety-degree angle.

An alternative embodiment 100 of the present invention is shown in FIG.8. This embodiment 100 is useful where the device 104 needing grip 100is a long, relatively thin solid. For example, small experimental andtoy robots may have legs consisting entirely of solid heavy piano wire.In this case, it is not practical to form a hole in device 104 as wasdone in FIG. 1. Rather, a spiral wound plug 102 is formed around thecircumference of device 104.

The process for forming plug 102 is shown in FIG. 9. As shown in thatfigure, the device 104 is used as the core around which a sheet 120 ofmaterial is tightly wrapped to form the plug 102. The figure also showsthat it is possible that the device 104 extends almost completelythrough the spiral plug 102. This is not necessary, however, and aneffective grip 100 can be created where the device does not extend allthe way through the plug 102.

It is necessary to secure the plug 102 to the device 104 to prevent thegrip 100 from falling off during use. In the preferred embodiment, thisis accomplished by coating the portion of the device 104 that forms thecord of plug 102 with a flexible adhesive 122. One adhesive suitable forthis purpose is “Pliobond,” a trademark of Ashland Oil, and marketed byW. J. Ruscoe Company (Akron Ohio 44301).

This same adhesive can be used to prevent the core 102 from unravelingduring use by applying a strip of adhesive 122 directly to the sheet 120prior to rolling. Ideally, the adhesive strip 122 runs along the lengthof the sheet 120 along side 124 and side 126, as shown in FIG. 10. Bylimiting the adhesive only to the side 124 of sheet 120 and not thecontact side 128, the portion of the core 102 that engages with anobject during use is free to separate into the separate layers of thespiral. Meanwhile, the adhesive along side 126 prevents any unravelingof this exposed edge.

Alternatively, the plug 102 could be held on device 104 via an elasticband or tape. Such a band would wrap around the plug 102 near side 124,and could also serve to prevent the unwinding of plug 102.

Grip 100 differs from the first embodiment grip 10 shown in FIGS. 1though 4 in the existence of an angled edge surface 128 that engageswith the environment. As seen in FIGS. 10 and 11, this edge surface 128is formed by cutting a long side of the rectangular rubber-like material120 at a dihedral angle (other than ninety degrees) from the surface.This produces a softer edge 128, which is more capable of gripping a wetsurface than the edge found in grip 10.

The invention is not to be taken as limited to all of the above details,as modifications and variations may be made without departing from thespirit or scope of the invention. For instance, although the abovedescription generally refers to the device as a walking assistancedevice or robotic appendage, the present invention could be used on anydevice that has need of a slip-resistant point of contact with itssurroundings. Consequently, the invention should not be limited by thespecifics of the above description, but rather should be limited only bythe following claims.

1. A gripping tip on a device comprising: a) a distal end of the devicehaving an area forming a hole; and b) a spiral plug having a first andsecond end and a plurality of lamina formed from a sheet of elasticmaterial, the first end of the spiral plug fixed within the hole in thedistal end of the device, and the second end of the spiral plugextending beyond the hole.
 2. The gripping tip of claim 1, wherein thedevice is selected from the group consisting of a prosthetic walkingdevice and a robotic appendage.
 3. The gripping tip of claim 1, whereinthe elastic material is chosen from the set consisting of rubber andpolyurethane.
 4. The gripping tip of claim 1, wherein the elasticmaterial has a coefficient of friction similar to or greater thanrubber, an elasticity similar to or greater than rubber, and adurability creating a service life at least half as long as rubber. 5.The gripping tip of claim 1, wherein the sheet of elastic material has aplanar main surface and a length-wise edge found at the second end ofthe spiral plug, wherein the length-wise edge is cut at an angle otherthan perpendicular to the planar main surface.
 6. A gripping tip on adevice comprising: a) a distal end of the device; and b) a spiral plugwrapped around and affixed to the circumference of the distal end of thedevice, the spiral plug having a plurality of lamina formed from a sheetof elastic material, the lamina being bound together at a first end ofthe spiral plug.
 7. The gripping tip of claim 7, wherein the spiral plugis affixed to the distal end of the device via adhesive bonding, andfurther wherein the lamina are bound together at the first end viaadhesive bonding.
 8. The gripping tip of claim 7, wherein the device isselected from the group consisting of a prosthetic walking device and arobotic appendage.
 9. A gripping tip on a device in contact with asurface comprising: a) spiral plug having spiral lamina made from awound sheet of elastic material, the spiral lamina having a point ofcontact surface; and b) affixing means for affixing the spiral plugmeans to an environmental contact point of the device.
 10. The grippingtip of claim 9, wherein the device is selected from the group consistingof a prosthetic walking device and a robotic appendage.
 11. The grippingtip of claim 9, wherein the elastic material is chosen from the setconsisting of rubber and polyurethane.
 12. The gripping tip of claim 9,wherein the elastic material has a coefficient of friction similar to orgreater than rubber, an elasticity similar to or greater than rubber,and a durability creating a service life at least half as long asrubber.
 13. The gripping tip of claim 9, wherein the point of contactsurface of the spiral plug is relatively planar.
 14. The gripping tip ofclaim 9, wherein the point of contact surface of the spiral plug isconcave.
 15. The gripping tip of claim 9, wherein the point of contactsurface of the spiral plug is convex.